Major League Baseball will implement a 20-second pitch clock for spring training games, and sources told ESPN that adding it for this regular season is a real possibility.

MLB announced the parameters for the clock in spring training Friday, outlining an easing-in period early in spring training during which the clock will operate without penalty for pitchers or hitters who run afoul.

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Aiming to speed up the pace of play in baseball, Major League Baseball commissioner Rob Manfred says the league will begin implementing pitch clocks in spring training games.

MLB says the pitch clock will not be enforced during games this weekend.

"Later in spring training," the league said in a release, it could instruct umpires to assess ball-or-strike penalties for clock violations.

The league continues to negotiate with the MLB Players Association about the possibility of implementing the clock in the regular season this year, but commissioner Rob Manfred can unilaterally impose a clock should the talks fall apart.

A pitch clock, which the league hopes will shave significant time off the average game time of 3 hours, 4 minutes in 2018, has been used in the minor leagues since 2015.

After averaging 22 seconds between pitches in 2017, MLB has proposed a 20-second pitch clock for the 2018 season to shorten games. Last season, MLB games took an average of 3 hours, 5 minutes to complete -- a record. AP Photo/Bill Wippert

The clock does not run on the first pitch of a plate appearance and starts when the pitcher receives the ball from the catcher. If the batter isn't in the box with five seconds left on the clock, umpires can assess him a strike. The pitcher must begin his windup or come to a set position before the expiration of the clock to avoid being penalized a ball.

Other details include:

The clock is reset to 20 seconds when the pitcher steps off the rubber or attempts a pickoff

The clock is not used on the pitch following a foul ball, a mound visit and an umpire calling timeout (except when replacing a ball in the dirt)

The pitcher must be in the dirt circle surrounding the mound and the catcher in the catcher's box for the clock to start